This invention relates to the manufacture of material with a fusible backing in general and more particularly to an improved method and apparatus for making each fusible material using a dry printing process.
Fusible interlinings are universally used in the manufacture of various articles of clothing. In general, such interlinings comprise a lining substrate, e.g., woven fabric, nonwoven, paper knitted fabric, etc., having polymeric material deposited thereon to permit the fusible interlining to be attached to the garment without the need for sewing by means of fusion through simultaneous heating, pressing or the like. Similarly, fusible backing is used in making iron-on patches and the like.
Various methods have been developed in the prior art for making such fusible interlinings and the like, i.e. for applying the polymeric material to a substrate. Two general types of processes have been used. One is a random or scatter application of the polymer and the other method a discrete or controlled application. Most universally used is the random method in which a large number of particles are applied on a moving web. The polymer particles of a relatively large size are usually gravity fed from a feeder hopper located above the moving web which forms the substrate fabric. After being randomly coated with these particles, the web then passes under a heat source where the polymeric material is heated to its tackifying or melt point, after which it is calendered or pressed, cooled and then rolled up. The process is relatively simple and has been used to produce great quantities of fusible interlinings over the years. However, even with the development of highly usable polymeric materials such as polymide, tetpolymers, polymers, HDPE, urethanes, etc., the optimum application and functioning of a scatter product are limited because of the random laydown and the large particle size.
Discrete or controlled methods of applications are much less common even through the fusible product is superior in function and application. The primary reason for this is the increased difficulty in producing the fusible lining using known methods. In general, the controlled methods are printing methods. Both wet and dry printing methods have been used. A summary of the methods used is given in an article entitled "Copolymeric Nylon Powders for Fusing Textiles" by Schaaf in the November 1972 issue of American Dyestuff Reporter. More detail is given in a similar article by the same author titled "Lannion sin costra" reprinted from Textiles Panamericanos. In one method known as the powder point method a dry powder is doctored onto an engraved steel roll. The engraved dots are filled with the dry powder. The substrate is preheated and then pressed against the cool engraved steel roll causing particles of polymer to stick to the heated substrate so that the dry powder is lifted out of the engravings. Thereafter, the substrate with the polymer still virtually a powder moves into an area of high heat, normally an infra-red radiant heating system where the polymer is reheated to a high temperature to bring it to a semiplastic state after which calendering or pressing completes the process of attaching the molten polymer to the substrate. Even this process which comprises a large number of steps and results in a better product than the random method, has disadvantages. Since the polymer is primarily heated from above, the additional calendering or pressing step is necessary. Even with this step, the binding of the polymer to the substrate fabric does not reach an optimum. The above mentioned article from Textiles Panamericanos does describe a powder point process in which the engraved steel roll is followed by a heated roll.
A silk screen method is also known. An aqueous paste is squeezed through a rotary screen equipped with an adjustable squeegee. The material is then heated or sintered in an elongated infra red heating apparatus. In an alternate of this method power is dusted on the substrate resulting in a random application before heating. This arrangement requires a great deal of space and still does not obtain optimum bonding of the polymer material to the substrate. Typically infra-red ovens are 20 to 30 feet long.
In view of these variaous difficulties with prior art processes, the need for an improved process which is simpler and insures adequate bonding of the polymer to the substrate becomes evident.